Electrical signal distribution system



y 14, 1 E. A. NEWMAN r-:r AL

ELECTRICAL SIGNAL DISTRIBUTION SYSTEM Filed Feb. 8, 1951 soov zoov+2dov Patented July 14, 1953 I SIGN SYS - TRIBUTION Edward Arthur Newman, f}1eddington, .Donald Watts Davies, 'Southsea, and .Ronald Fraser Braybrook, South Kensington, London, England, assignors to National Research Development- Corporation, L

corporation 7 ondon,England, a British immanent-sly 8, 1j 951 ,.seria1;1vo;:209,94c "I'n 'Great'Britain February 28, 1950 This invention relates to distribution circuits that is to say circuits adaptedto open oi-close) one of 2 channels in 'accordancawith a particular permutation of polarities, of 'n voltages applied tothecircuit.

Such circuits are used for example in digital computing systems for "selecting channels in accordance with numbers in instruction words and an example of a distribution circuit and its method of operation is described in -Unitedstates patent application No. 202,615 by James H. Wilkinson, filed December 26, 19 50, with reference to Figure 15 of the drawings of that specification.

These circuits are also described on pages 40 to "43 and 377 to 37s in High-Speed Computing I Devices" 'wr'itten by the Staff of EngineeringResearch Associates and published in 1950 by Mc- Graw-Hill Book Company. 7

Distribution circuits generally comprise a network of resistances, usually called a matrix or "the selected output lead is V while the highest voltage on certain other output lines is Vfll/n'l where n is the order of the matrix. Thus the discrimination factor or the matrix-is 1hr,

For example in a matrix of order five if the applied potential differences are each "30 volts then the voltage on the selected output line will I b .30 volts the highest voltages occurring-on certain other output lines will be 24 volts, giving 6 volts discrimination. l a

It is not convenient to have a seriesoflines with various voltages on them for controlling a series of gates and 'thepresent inventionis coricerned with an output circuit for a 'rnatrixwhich will give one predetermined voltage on a selected output and another predetermined voltage on-all the remaining outputs.- e V v The invention also provides acir-cuit which-de- 1 :1 Claims. (01.- 250 27 distribution circuit and comprising a series of V thermionic valves having separate anode loads and input circuits but a common cathode load, "the valves being arranged to be controlled separately at their input circuits 'by the output voltages from a matrix circuit so that only one selected valve in the series passes anode current when the distribution circuit is setup.

lfhe common cathode load may be a simple resistance but when the matrix is used in a computing system it is convenient to render it operativ'e only during certain periods. Accordingto a feature of the inventionftherefore, the common pends for its operation on the difference in -po tential between the selected output line from-the matrix and the output lines of "next highest ,po-

tential and thus overcomes to a great extent irregularities in operation due to variationsnin provided an output "circuitarrangement for a cathode load comprises a further thermionic valve circuit arranged to be conductive only when the distribution circuit is required to operate.

"I'he invention will now be described withref- 'er'ence to the accompanying drawings of which:

Figure 1 illustrates one embodiment of the inventionand I "Figure 2 illustrates a detail of a modified embodimentof the invention.

' InFigure 1, there is shown a matrix I of order n the output leads of which feed the control grids "of 2" (or as many as there are circuits to be controlled by the matrix) valves of which three are shownat 2, 3 and 4. The cathodes of all valves -sr'ich as 2, 3 and 4, are connected through a comi'nori load- 5 to a source of low potential, say 300 volts. As indicated, this load my be a resistance. The valves such as 2, 3 and 4 are connected through separate anode loads to a source of high potential, say +300 volts.

When working with very short duration pulses, the anode loads and coupling circuits of the varigous ivalvesmay require the usual de-coupling and correcting'impedances. Thus the anode loads of the valves such as 2, 3 and 4 may each comprise, as shown in the drawing, 360 microhenries in series with 4,700 ohms and 22,000 ohms, which is inparallel with 0.01 microfarad.

{suppose now that theinputs to the matrix I are such that the potential of the grid of valve 2 is somewhere near earth potential, and is greater than the potential on the control grid of any of the valves by a potential suiilcient to out the valves off, then valve 2 alonewill be conducting and its anode potential will be at some predeterminedlevel while the anode of all the other valves will be at some predetermined higher level.

The series of valves such as 2, 3 and 4 feed a corresponding series of gate circuits from their anodes and the gate circuit associated with the' valve 2 is shown at 9 the other gates are omitted "from-thepicture forthe sake of clarity.

V 3 A suitable gate circuit 9 comprises two valves I and II having a common cathode resistance connected to a source of negativebias of 300 volts. The anode of valve H is connected to earth and the grid thereof is connected to the anode of valve 2 through resistance 30 and capacitance 3| in parallel and to a bias of 300 The cathodes of volts through resistance I4.

,. tiVe 4 prising a distribution matrix having a plurality of outputs, a plurality of thermionic valves having indivitjlual output circuits and individual grid circuits but a common cathode load, means connecting each of said matrix outputs to a respecindividual grid circuit of one of the thermionic valves, and a gating circuit connected to the individual outputs of each valve, each gating valves I5 and I6 are connected to the anode of valve I0 and the grids of these valves are respectively potentials of 0 andf+7 volts. The anodes I of valves I5 and I6 are biased at +200.volts.

If, then, a signal of +15 volts is applied to the grid of valve I5 at the time valve I0 is made conducting due to the application of a negative pulse from valve 2 to the grid of valve I I, a current will "circuit including thermionic valve means re- 10 sponsive tovoltagechanges in the said output to which the gating circuit is connected.

22. An electrical signal distribution system as a 5 claimed by claim l'wherein the gating circuit inflow through valve I5 and an output pulse will be transmitted from the anode of valve I5.

The gate 9 is fed by the valve 2 through a resistance of 470,000 ohms in parallel with 470 micromicrofarads to match the anode load, of the .-valve.

i In one particular embodiment of the invention the valves had a grid base of about ivolts and the various resistances and supply-potentials were arranged to give the working potentials indicated in the drawings.- l

The common cathode load 5 may be a simple resistance but in some uses of the invention it .may be convenient to replace this resistance by a circuit which becomes conducting only during certain periods. Such a circuit is shown in Figure ;2. This circuit comprises two valves I! and- I8. having separate anodecircuits but a common cathode load I9 leading to'a point of low potential, say 300 volts. The control grid of the valve I8 is held at ,say -200 volts while the control grid of the valve 'il, is'normally held at 210 volts but is; caused-to rise to 190 volts and so to become conducting during periods in which the matrixcircuit is to operate. The output circuit in Figure 1 forms the anode load of the valve I1 and thus becomes operative only when valve l7 is conducting, r

. The circuit as so far described is suitable for switching the matrix output circuit in most cases but when the pulses to be dealt with occur at a .very highfrequency (e. g. microsecond pulses occurring at. a repetition frequency of a mega- 1 cycle) two further valves and 2| may be used.

These? valves 20 and El have their cathodes. and grids connected and controlled in the same manner as the valves I1 and I8 but have in their anode circuits inductive loads 22 and 23 which ,give sharp negative and positive voltage peaks as thevalves ZIl-and 2| are switched on and off. ihe inductive loads 22 and .23- may be shunted by resistances (as shown) to control the amplitude and attenuation of the voltage peaks.

These voltage peaks are applied to two valves 24 and 25 biassed to be operated by the positivegoing peaks only. The valve 25 is a cathode follower and. applies the positive peak (the off circuit of Figure l.

valve. 24 is connected normally and applies-the positive peak (the on peak) from the valve 2| as, a negative voltage pulse to the common cathfodes of-the matrix outputcircuit.

- What we claim is:

' 1. An electrical signal distribution system comcludesa first and a second thermionic valve, the grid of the firstvalve being connected to the said individual output and the anode of the first valve .being "connected to earth and the cathodes of both valves" being connected to a common bias source; a third and a fourth thermionic valve having their cathodes connected to the anode of ,the second valve, the grid of the third valve having a small-positive bias impressed thereon and means connectedto the: anode of the fourth valveto transmit a signal in response tea-signal impressed on thegrid of the fourth valve at a time when the secondvalve is conducting due to the application of a negative pulseto the grid of the first valve.

- ,3. An -electrical signal distribution system as claimed by claim 1 wherein the common cathode load includes. a I plurality of thermionic devices connected to become conductive and'make the cathode, load operative in response to asignal applied thereto simultaneously with the application of a'signal to thelmatrix. l

I system com- ,prisinga matrix having a-pluralitypf outputs, a

1 A n el'eetrica-lsignal distribution respective;thermionic valve connected to each output, gating circuitry connected to each valve .to be readiedfor signal transfer by a voltage applied thereto from the valve when the valv is conducting; and a common cathode load for all the said valves,- the said load including firstand second paried thermionic valves each having .anode,- grid. and cathode, the, first anode-being ,connected tothe cathodes of the valves connected to the matrix outputs; the second anode :being grounded, the :two cathodes having a common connection to' aysource of considerable negative potential, the grids beingat aless negative potential than the cathodes and the second grid being somewhatless'negative than the first grid, whereby-the secondvalve will-normally be conductive; third and fourth paired thermionic valves each having anode,grid and cathode, both the third and-fourth anodes being grounded, the oathodessbeingat the same negative potential as the first and second cathodes, and the third and .fourthgrids being a-tthe same. potentials as the first and second grids, respectively, and like im- Dedances connected between each of the third and fourth anodesand ground; a fifth thermionic 'tub 'having anode-grid andcathode, there being small negative bias on the fifth grid, means connecting the fifth grid to a point between the third anode and its associated impedance, and means c'ohnectin'gthe fifth cathode to the cathodes or the valves, connected to the matrix outputs a sixth"thc errnionic valve having anode, grid {and cathode, there being a small negative bias on the sixth grid, means connecting the sixth grid to a :point, between thefourth .anode and its associated impedance, the sixth cathode being grounded an impedance. connecte'dito thesixth connecting the sixth anode to the cathodes of the valves connected to the matrix outputs.

5. An electrical signal distribution system comprising a matrix having a plurality of outputs, and means connecting each of said outputs to the grid of a respective first thermionic valve having anode, grid and cathode, an anode input impedance; second and third paired thermionic valves each having anode, grid and cathode, the cathodes being connected through a common cathode load to a source of large negative bias, the two grids being at negative potentials less than that of the source of cathode bias and the second grid beingisomewhat less negative than the third grid, the second anode being grounded whereby the second valve will normally be conductive and the bias on the cathodes will be higher by a value equal to the drop across the cathodeirnpedance than the poential of the source to which they are connected; fourth and fifth thermionic valves each having 1 anode, grid and cathode, common means connecting the fourth andfifth cathodes to the an- I ode of the third valve, the fourth and fifth anodes having strong positive bias impressed thereon, the grid of the fourth valve being somewhat more positive thanthat'of the fifth valve so. that when the third valve is conducting the fourth valve will also conduct but the fifth valve will become conductive when a positive signal voltage higher than the bias on the fourth grid is impressed upon the fifth grid; means connecting the grid of the second valve to a point 1 between the anode and the anode impedance of the first valve whereby when said first valve 3- conduots the grid of the second valve is made more negative so that the third valve becomes conductive; and a common cathode load for all the valves connected to the matrix outputs.

6. An electrical signal distribution system, comprising a plurality of like thermionic valves, means selectively to place any one of said valves in conducting condition; gating circuitry operatively associated with each of said valves, the

gating circuitry having a first pair of triode Q thermionic valves, a common connection to the cathodes of the valves of this pair; .a second pair of triode thermionic valves having their cathodes connected in common to the anode of a valve of the, first pair, the anode of the other r valve in the first pair being grounded, and means connecting the grid of said other valve in the first pair to the anode of a respectively associated valve of said plurality; and a common cathode load for all the valves of said plurality, including a third pair of triodethermionic valves having a common connection to their cathodes, the anode of one valve of the third pair being connected to ground and the other anode of the third pair connected in common to the cathodes of all the valves of said plurality, a fourth pair of triode thermionic valves having a common connection to their cathodes and a peaking impedance connected to each anode and to ground, a cathode follower valve having its cathode connected to all the cathodes of said plurality of valves and means connecting its grid to a point between the anode and the peaking impedance of one valve of the fourth pair,- and a thermionic valve having its cathodegrounded, means connecting the grid of the last-mentioned valve to a point between the anode and the peaking impedance of the other valve of the fourth pair, an anode impedance connected to'the anode of the last mentioned valve, and means connecting all. the cathodes of the valves of said plurality to the anode of the last-mentioned valve.

7. An electrical signal distribution system, comprising a plurality of like thermionic valves, means selectively to place any one of said valves in conducting condition; respective gating circuitry responsive to a signal from each of the valvestof the plurality, each circuitry having a first pair of triode thermionic valves, a common connection to the cathodes of the valves of this pair; a second pair of triode thermionic valves having their cathodes connected in common to the anode of a valve of the first pair, the anode of the other valve in the first pair being grounded, and meansconnecting the grid of said other valve'in the first pair to the anode of the respective valve in the said plurality; and a common cathode load for all the valves of the plurality, including a third pair of triode thermionic valves having a common connection to their cathodes. the anode of one valve of the third pair being connected to ground and the other anode of the third pair connected in common to the cathodes of all the valves of said plurality.

EDWARD ARTHUR NEWMAN. DQNALD WATTS DAVIES. RONALD FRASER BRAYBROOK.

References Cited in the file of this patent V UNITED STATES PATENTS Number Name Date 2,457,819 Hoeppner Jan. 4, 1949 2,486,391 Cunningham Nov. 1, 1949 2,510,989 Lichtman et a1. June13, 1950 2,521,952 Stephenson Sept. 12, 1950 2,577,141 Mauchly et al. Dec. 4, 1951 FOREIGN PATENTS Number Country Date 635,475 Great Britain July 16, 1945 

